Various kinds of RF (radio frequency) receiving coils matching their use can be used for magnetic resonance imaging apparatus in recent years. Some kind of such RF receiving coils is formed by lots of coil elements. A particular coil element is chosen from lots of coil elements in accordance with an imaging target part of a patient or an imaging method. Then, a signal received by the chosen coil element is connected to a receiving processor system on a successive stage.
In order to choose a desired number of desired coil elements from lots of coil elements, the magnetic resonance imaging apparatus is provided with a multichannel RF signal switching device called a matrix switch, as disclosed in Japanese Unexamined Patent Publication No. 2009-278459.
The matrix switch has e.g., 128 channels of input ports and 32 channels of output ports. The respective coil elements are each connected to each of the input ports. Thus, e.g., up to 32 received signals are selected from signals received by up to 128 coil elements, so as to output the 32 selected signals to any of the output ports of 32 channels. The received signals outputted from the matrix switch are provided to receiving circuits on a successive stage in parallel.
One of key performance indicators of the matrix switch is inter-channel isolation. Poor inter-channel isolation causes signals received by different coil elements to interfere with one another resulting in a degraded SNR, etc., and degraded image quality.
An imaging method called parallel imaging for which signals of plural coil elements are used is known. Poor isolation among the plural coil elements may possibly cause not only degraded image quality but an error in an expansion process included in the parallel imaging.
The isolation tends tube low between adjacent input ports or adjacent output ports of the matrix switch in particular, and needs to be improved.